JPS6239B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides control of flapping of helicopter blades,
In particular, it concerns composite elastic boss structures with non-linear spring characteristics.

It is well known to provide resilient bosses in helicopters to counteract and minimize the tendency of the blades to flap during flight. US Patent No.
No. 3,807,896, a pair of concentric tubes extend along the axis of oscillation and are connected to the vanes and struts, respectively, so as to counteract the flapping of the vanes by a torsional action. According to U.S. Pat. No. 3,804,552, an elastomeric bearing is mounted between a rotor frame flange that rotates with each blade about the flapping axis and a strut flange that is fixed to a strut.

The presence of the elastic boss creates a force that counteracts the flapping. Modulus of elasticity or spring constant
The struts cause strong or weak vibrations of the fuselage frame depending on the rate. A high modulus is desirable during flight maneuvers to prevent excessive flapping. Under level flight conditions, a low modulus is desirable to minimize vibration and increase stability.

Flight motion is the motion of an aircraft with acceleration.

According to the present invention, a composite elastic boss device is provided that has a low modulus of elasticity at small flapping angles. In this boss device, the elastic modulus increases starting at a predetermined flapping angle. The increase in elastic modulus can be tailored to the desired transition characteristics to avoid or minimize hard contact between the rotor and strut during high flap angles.

According to the present invention, a composite resilient boss structure is provided to control flapping of a main helicopter rotor blade. This structure applies a restraining force that has a low elastic modulus at low flapping angles and has a high elastic modulus at flapping angles larger than a predetermined flapping angle.

In particular, the main helicopter rotor blades are connected to the main rotor by means of a member that exerts a linear constraint force with a low modulus of elasticity. In addition, a resilient elastomeric block-like member mounted for rotation with the rotor around the flapping axis provides a restraining force exhibiting high modulus characteristics prior to the violent contact between the rotor and the strut. .

In one embodiment of the invention, the elastic modulus of the resilient elastomeric block increases as the blade flapping angle increases for angles beyond a predetermined flapping angle.

According to the invention, the elastic modulus of this elastic elastomeric block is controlled by changing the area of the contact area between the elastic elastomeric block and the struts, so that the elastic modulus is non-linear with increasing flapping angle. An increase in shape begins to occur.

Embodiments of the strut-frame joint of the present invention will be described in detail below with reference to the accompanying drawings.

1 and 2, there is shown a strut frame joint 10 forming a composite resilient boss structure according to the present invention.

The column joint 10 includes a pillow block 11 to which an outer support plate 12 is fastened by bolts 13. The elastic boss plate 14 is fastened to the boss trunnion 15 by bolts 16. The pillow block 11 is connected to the boss trunnion 15 by an elastomeric bearing 17 formed in a cylinder 18 within its bore. The cylinder 18 is fastened to the boss trunnion 15 by bolts 16.

The elastomeric bearing 17 is connected to the pillow block 1.
It consists of a laminated elastomeric cylinder with a thin metal cylinder inserted between each cylinder 1 and an inner cylinder 18.

The frame 19 is integrally formed with the pillow block 11 and supports the annular body 20 on the lower surface of the frame 19. A resilient elastomeric block 21 is bonded to the inner wall of the annulus 20 concentric to the rotor strut 22. The inner surface of the annular body 20 is the boss trunnion 1
It has a conical shape with its apex located on the axis of 5.

The flange 14a of the resilient boss plate 14 extends between the outer support plate 12 and the inner plate 23 adjacent the pillow block 11. The outer support plate 12 and the inner plate 23 are fixed to each other by spacers 24 and fastened to the pillow block 11 by bolts 13. Elastomeric shear pad 2
5 and 26 are bonded to mutually facing surfaces of the outer support plate 12 and the inner plate 23, and to each surface of the flange 14a.

According to the invention, the elastomeric bearing 17 comprises:
This allows flapping of the helicopter rotor blades about the axis of the boss trunnion 15. Outer support plate 12 and inner plate 23 fixed to pillow block 11
rotates together with the pillow block 11 when the blades flap. When the outer support plate 12 and the inner plate 23 rotate, the elastomeric shear pad 2
5 and 26 are subjected to shear force because the flange 14a is fixed to the trunnion 15.

As the flapping angle increases, the elastomeric block 21 approaches the rotor strut 22. When the resilient elastomeric block 21 contacts the rotor strut 22, harsh contact between the rotor strut 22 and the strut frame joint 10 is avoided or minimized. The elastomeric block 21 acts as a resilient boss and applies an anti-flapping force that can be easily adjusted to meet design criteria.

FIG. 3 shows a diagram of the forces produced by a preferred embodiment of the invention during the flapping of a helicopter rotor blade.

Elastomeric bearing 1 with increasing flapping angle
The restraining force caused by 7 is illustrated by line 30. This restraining force increases monotonically as the flapping angle increases. The combined effect of the elastomeric bearing 17 and each elastomeric shear pad 25, 26 is illustrated by line 31. This combined restraining force is substantially linear but higher.

When the flapping angle of the rotor assembly or strut frame joint 10 is large enough to cause the resilient block 21 to contact the rotor strut 22, the combined restraint force will be reduced by line 32 for one shape of the resilient elastomeric block 21. An example is given. The composite resilient boss structure thus creates a linear restraining force illustrated by line 31 until the resilient elastomeric block 21 associates with the rotor strut 22 as indicated by point 33. This restraining force is then line 32
increases at an even higher rate, as exemplified by

Figure 4 shows the support plate 12 and flange 14a in Figure 2.
and a modification of the elastic boss consisting of a pad 26.

As shown in FIG. 4, a short cylinder 40 is fastened together with a plate 42 to the outer end of the boss trunnion 41 by bolts 43. Pillow block 44 houses the bearing of boss trunnion 41. The outer cylinder 46 is
It is fastened to the block 44 with a bolt 48. Elastomeric cylindrical shear pad 50
is adhered to the outer surface of the cylinder 40 and the inner surface of the cylinder 46.

In operation, as the pillow block 44 rotates around the boss trunnion 41, the shear pad 5
A shear force is applied to 0.

5 and 6 show a modification of the composite elastic boss structure of FIGS. 1 and 2. FIG.

In particular, the rotor assembly 60 is mounted for rotation with the main rotor strut 61. The rotor assembly 60 consists of a pillow block 62, a frame 63 integral with the pillow block 62, and a grip 64 connecting a helicopter rotor blade (not shown) to the frame 63.

A block or ring 65 surrounds the column 61. A molded elastomeric ring 66 is adhered to the inner surface of block 65. The upper and lower surfaces of the block 65 are conical and taper to the tip associated with the column 61. As is clear from FIG. 6, the annular body 66 is shaped to contact the support column 61 at a point perpendicular to the flapping axis. The annular body 66 is a semi-annular body 65, 65, respectively.
It is preferable to form it into two halves having similar shapes and bonded to a. Each semicircular body 65, 65a
are connected to each other by bolts 67 and fastened to frame 64 by bolts 68. Each split or half-ring 66, 65a allows the non-linear resilient boss to be installed in existing aircraft without undue modification.

Unlike elastomeric block 21 of FIG. 1, each elastic block or split annulus 66 produces a non-linear restraining force as illustrated by curve 34 of FIG. The non-linearity is selected by adjusting the shape of the annulus 66. The initial force is small due to the slight contact of the tip, but increases as the contact area with the support column 61 increases. Of course, the linear elastic boss is of the shape described in the aforementioned US Pat. No. 3,807,896. That is, the restraining force generated by the composite elastic boss structure consisting of the elastomeric bearing 17, the elastomeric shear pads 25, 26, and the elastic block 66 shown in FIG.
Line 3 for a low flapping angle as shown to the left of 3.
1. When the rotor assembly 60 swings as the flapping angle increases, the resilient block or ring 66 deforms toward the strut 61. In such a state, a curve 34 appears to the right of point 33.
It is shown by. The non-linear restraining force in this case is generated in opposition to the flapping of the helicopter rotor blades.

That is, the modulus increases linearly from a low value under flight conditions such as stopped flight with low flapping angles, and increases non-linearly rapidly during flight conditions with high flapping angles. A composite elastic boss device is obtained.

Although the present invention has been described in detail with reference to its embodiments, it is obvious that the present invention can be modified in various ways without departing from its spirit.

[Brief explanation of the drawing]

Fig. 1 is a side view showing one embodiment of the strut frame joint of the present invention, with a part of the axial cross section;
FIG. 3 is a cross-sectional view taken along line -2 and a line diagram showing the action of the strut-frame joint of the present invention. 4 is an axial sectional view of a modification of the main part of the strut frame joint shown in FIG. 1, FIG. 5 is a side view showing another modification of FIG. FIG. 3 is a plan view showing a part of the figure in horizontal section. 10... Prop frame joint, 11... Pillow block, 12... Outer support plate, 14... Elastic boss plate,
14a...flange, 15...boss trunnion,
17...Elastomer bearing, 19...Wall, 2
0... Annular body, 21... Elastomer block, 22... Rotor strut, 23... Inner plate, 2
5,26... Elastomeric shear pad.

Claims (1)

[Scope of Claims] 1. In a strut frame joint 10 that is attached around a rotor strut 22 so as to rotate together with the rotor, and is used to control the flapping characteristics of a helicopter blade, (a) the rotor strut 22 is provided with: (b) a pillow block 11 having an outer support plate 12 and an inner plate 23 and connected to said boss trunnion 15 using an elastomeric bearing 17 disposed therein; ) an annular body 20 with an elastomeric block 21 concentric to said rotor strut 22 and a frame 19 formed integrally with said pillow block 11;
(d) an elastic boss plate 14 having a flange 14a extending between the outer support plate 12 and the inner plate 23 and fixed to the boss trunnion 15; (e) the flange 14a and the outer support plate 14; Board 12
(f) an elastomeric shear pad 26 bonded to mutually opposing surfaces of the flange 14a and the inner plate 23; The elastomeric bearing 17 and the elastomeric shear pads 25, 26 counter the flapping of the helicopter blades by a first restraining force, and when a flapping angle greater than a predetermined angle occurs, the elastomeric A strut frame joint in which the block 21 applies a second restraining force.